Valentine, J. W. Department of Geology, University of California, Santa Barbara, California.
Last reviewed:December 2019
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A major division of the animal kingdom comprising the phyla Hemichordata, Echinodermata and Chordata. Hemichordata consists of acorn worms (Enteropneusta) and a group of small-bodied, tentaculate forms (Pterobranchia). Echinodermata contains the starfish, sea urchins, crinoids (sea lilies) and their allies. The phylum Chordata includes the Urochordata (sea squirts and larvaceans), Cephalochordata (Branchiostoma, the sand lancelet, formerly Amphioxus) and vertebrates (see illustration). At one time, up to 10 phyla were included in Deuterostomia on the basis of shared morphological and developmental features; however, comparison of deoxyribonucleic acid (DNA) sequences indicates that most of those phyla are more closely allied to other groups. See also: Animal kingdom
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